Large containers, tanks or related vessels (often sized to hold between about 120 to 330 gallons of working fluid (i.e., product) material) are used to store and transport chemicals such as fertilizers, insecticides and herbicides that are used in agricultural and related industrial purposes. In one form, these containers are purpose-built from a generally one-piece plastic mold of a particular shape and dimension to enable convenient stacking for storage, as well as possessive of upstanding projections to provide protective placement of a crop sprayer, pump or other suitable liquid-dispensing apparatus; such containers are often colloquially referred to as mini bulk tanks. Another form is known as an intermediate bulk container (IBC), where a generally rectangular-shaped plastic material is housed within a complementary-shaped metal skeleton frame to provide a relatively rigid, structural container. Regardless of the configuration, the chemicals contained in such vessels are often concentrated and viscous, and are prone to stratification during storage, including the formation of a serum-like upper layer. In such circumstances, it is advantageous to agitate the contents prior to dispensing to ensure even distribution of the active materials within the working fluid. Furthermore, dedicated pumps may be included to help promote the aforementioned agitation, while an integral-like connection between the pump and container is established to further comply with sealing, anti-tampering and related fluid isolation requirements. Because the pumps are often placed at or near the place of fluid ingress or egress, environmental regulations may additionally require that the pump-to-container interface be sealed with tamper-resistant devices.
While conventional pumps return fluid back into the container, their ability to achieve thorough content agitation (and concomitant mixing) is limited; this is especially so for fluids such as those mentioned above that exhibit significant viscous- or serum-like upper layer formation or related stratification. Thus, in circumstances where thorough mixing is required, a user would have to defeat any tamper-resistant features by breaking the seal in order to gain access to the inside of the container as a way to install a portable mixer. Such activities could present a cleanup and disposal problem for any of the residual chemicals on the pump dip tube, mixer blade and other installed components, as well as expose personnel to potentially harmful fluids within the container. While other ways to enhance agitation, such as the introduction of compressed air or related fluid, are effective, they tend to add significant overall system cost and complexity in the form of additional pumps, valves and piping. Furthermore, there are limits on how such agitating fluids may be introduced into a pump and tank assembly, as many pumps may suffer cavitation-related damage (or have their effectiveness significantly curtailed) by having to process fluids where both gaseous and liquid phases may be present. Moreover, there are some contained fluids that suffer adverse reactions when exposed to air or related agitants.
Diaphragm pumps rely upon the cammed, wobbling or nutating motion of a pistoned plate-like member for converting the rotary movement of an accompanying motor into reciprocating pumping movement imparted to a fluid that has been introduced into a pumping chamber that is partially defined by the diaphragm. In one typical form, the diaphragm is made from a flexible material that defines multiple individual pumping chambers arranged circumferentially such that the suction and discharge of the fluid being pumped correspond to axial and tangential flow into and out of the pump. The present inventor has recognized that such pumps are particularly advantageous for use in conjunction with IBCs and mini bulk tanks, particularly those used in for agricultural and chemical process shipping, storage and dispensing. The present inventor particularly recognized that the diaphragm pump is well-suited for use on a viscous fluid environment and is relatively impervious to cavitation, making it a good way to provide agitation and related mixing to stratification-prone contents within such IBCs or purpose-built containers. Nevertheless, there remains a need to provide enhanced agitation and related mixing in such closed containers where stratification-prone liquids are stored.